Pulse oximetry is a non-invasive method allowing a monitoring of the oxygenation of a patient's hemoglobin using a pulse oximeter. A sensor is placed on a thin part of a patient's body, usually a finger tip or earlobe. Red light with a wavelength around 650 nm and infrared light with a wavelength around 850 to 940 nm are sequentially passed through the patient to a photodetector. The changing absorbance of each of the two wavelengths is measured, allowing determination of the absorbances due to the pulsing arterial blood alone, excluding venous blood, skin, bone, muscle and fat. Based upon the ratio of changing absorbance of the red and infrared light caused by the difference in color between oxygen-bound (bright red) and oxygen-unbound (dark red or blue in severe cases) blood hemoglobin, a measure of oxygenation (the percent of hemoglobin molecules bound with oxygen molecules) can be made. This is also called SpO2 monitoring in the art.
Camera-based SpO2 monitoring is conventionally realized by two monochrome cameras with corresponding optical band-pass filters, but this is non-practical due to the required alignment (i.e. spatial alignment of the images from two or more sensors), complexity and costs for many applications, such as applications in sports, home-use or for implementation in smart devices, such as mobile phones.